An Active Matrix Organic Light Emission Display (AMOLED) becomes one of candidates for the future display technology due to advantages of high image quality, short response time to a moving image, low power consumption, wide viewing angle, and ultra light and thin. In the current back plane technology for the AMOLED, technology for manufacturing a polysilicon layer comprises excimer laser annealing (ELA), solid phase crystallization (SPC), metal induced crystallization (MIC) and the like. And the excimer laser annealing (ELA) process is an only method for mass production of a polysilicon thin film for an active layer of a transistor in the back plane.
The excimer laser annealing process is a relatively complicated annealing process. For surface flatness of the polysilicon thin film, how to control grain size and grain uniformity is always a research focus in the excimer laser annealing process. Currently, an ordinary laser annealing process may cause the nonuniformity of polysilicon grains, significant roughness of the thin film (in an ordinary process, the thin film roughness at a partial place can be up to half or even more of a total thickness of the thin film), relatively small grain size of the polysilicon thin film, and uneven distribution. Because the number and the distribution of the polysilicon grains covered by a channel region of a low temperature polysilicon thin film transistor (a uniformity issue) and the surface flatness (the surface roughness) of the polysilicon thin film can directly influence electrical properties (mobility, leak current, the uniformity of the mobility and a threshold voltage and the like), how to manufacture the low temperature polysilicon thin film having smaller surface roughness and grains of large size with uniform distribution is an issue to be solved.